This proposal investigates the relationship between markers of angiogenesis in colorectal tumors and treatment outcome with a regimen containing bevacizumab, an anti-VEGF antibody. The proposal also explores the determinants of the biology of angiogenesis, the effects of its inhibition on tumor cell survival, and the sources of interpatient pharmacogenetic variability that may underlie treatment effects with 5-fluorouracil, oxaliplatin and bevacizumab. To accomplish these objectives, the proposal utilizes tumor blocks collected through the Eastern Cooperative Oncology Group (ECOG) Trial E3200, a randomized study of 5-fluorouracil, Oxaliplatin With or Without Bevacizumab. [unreadable] [unreadable]